1. Field of the Invention
The present invention concerns a method of gel-coating seed and an apparatus used therefor. More specifically, it relates to a method of coating a seed efficiently and continuously with a gel layer containing nutrients, sterilizers or like other chemicals, and having elastic property, in which only the surface layer of the gel is cured for protecting the seed and the seed is sphericalized and enlarged for improving the germination rate and facilitating seeding. The invention also relates to an apparatus used for practicing such a method.
2. Description of the Prior Art
There are various size and shape of seeds and those seeds of minute size or irregular shape can not be handled with seeders.
As a countermeasure, there have been developed coated seeds in which the periphery of a seed is protected with a coating material containing nutrients, sterilizers, etc. and the seed is sphericalized and enlarged for easy seeding.
In the conventional seed-coating, nutrient, sterilizers or like other chemicals are dressed to the periphery of a seed, or the periphery of a seed is coated with coating material such as clay or sugar incorporated with chemical to form a relatively hard coating layer.
The apparatus used for the seed coating is substantially in common with both of the methods.
That is, the apparatus generally comprises a spraying device for spraying a diluted aqueous solution of CMC (carboxymethyl cellulose) or gelatin as a binder to the surface of a seed and a coating pan for forming a coating layer around the seed while rolling the coated seed.
Accordingly, the coating procedure is separated into two steps in such an apparatus and continuous coating operation cannot be conducted.
There has been also developed an apparatus for conducting the seed coating operation by on step.
For instance, an apparatus using a rotary drum, instead of the coating pan, for applying or coating has also been put to practical use as described in Japanese Utility Model laid-Open Sho 59-146504 and 60-95811. However, although the apparatus can deal with a great amount of seeds, it creates a problem in that the apparatus cannot cope with the difference of the natures of seeds that vary depending on the kinds of plants. In addition, an external force exceeding an allowable level is exerted on the seed in view of the structure.
The prior art described above has the following problems.
(a) Dressing at the periphery of seeds varies greatly with respect to the shape and the thickness.
(b) Appropriate control for the thickness of the coating is extremely difficult and scattering of thickness may sometime lead to failure of germination.
(c) Since external force is applied to seeds in a mass-coating apparatus, it causes troubles such as injury or crack.
(d) It is difficult to apply coating by means of a coating pan for those seeds having a shape far from the spherical form.
(e) When a seed is sealed in coating, lack of oxygen may be caused.
(f) Since seeds of light weight can be scattered, the coating material will not be adhered thereto well by rolling (seed of light weight and minute size oscillate simply upon using vibration coating).
(g) There are soft coatings using such gel or gelatin-like material that swells when the seed contains water. However, there has not yet been known no coating the seed by using an aqueous gel that cures only at the surface layer.